1. Field of the Invention
The present invention relates to a metal-loaded zeolite catalyst for dehydrogenation of light alkane and a preparation method thereof.
2. Description of the Related Art
Due to the recent development of shale gas, the price of light alkane, especially propane, is rapidly stabilized. Shale gas contains a large amount of light alkane gas such as ethane gas, propane gas, and butane gas. So, the process of dehydrogenation for preparing light alkene such as propylene is in the spotlight.
The dehydrogenation of light alkane gas, particularly propane, is performed at a high temperature over 550° C. Since the catalytic reaction of dehydrogenation is performed at the high temperature, side reactions such as pyrolysis and coke generation are accompanied. The degree of such side reactions is a key factor to determine the selectivity and activity of a catalyst. The coke generation, which is one of the side reactions, reduces the overall reaction conversion rate of a catalyst by blocking the contact with the reactants by covering the active metal on the catalyst with coke. As the coke generation progresses, the pore inlet in the catalyst is clogged, and the accessibility of the reactant is greatly reduced due to the active metal present in the pores, leading to the rapid deactivation of the catalyst.
Dehydrogenation catalysts can be divided into two groups according to the active metal component, which are chromium oxide catalysts and platinum catalysts.
In the case of the chromium oxide catalyst (U.S. Pat. No. 6,797,850), the deactivation rate of the catalyst according to the coke generation is high, and thus the regeneration must be frequently occurred. Therefore, the lifetime of the catalyst is relatively short, compared with that of the platinum catalyst, and the chromium oxide catalyst has environmental problems due to the toxicity of chromium itself.
When gamma-alumina (U.S. Pat. No. 6,756,515) is used as a support to load an active metal component, the possibility of side reaction increases due to the high acidity of the alumina support itself and the possibility of changes in alumina phase during the reaction is also high and the specific surface area is significantly reduced due to the high reaction temperature, indicating that the structural characteristics can be changed. Alpha-alumina (U.S. Pat. No. 6,486,370) lowers the dispersibility of the active metal due to the low specific surface area and reduces the overall active area, indicating that it shows a low catalytic activity.
Most of the patents related to dehydrogenation catalysts informed so far have dealt with alumina, silica or silica alumina mixture as a support. Zeolite has a large surface area and a high thermal stability. In particular, zeolite exhibits excellent acid catalytic properties, so that it has been widely used in various reactions such as cracking, isomerization, and dehydration. However, studies on the dehydrogenation have been limited.